1. Field of the Invention
The present invention relates to a hood airbag device that deploys an airbag over the hood of a vehicle when the vehicle collides with an impact object.
2. Background of the Invention
Japanese Patent Application Publication No. JP-A-7-232615 discloses a hood airbag device in which a pair of left and right airbags is deployed over the hood of a vehicle. Stated briefly, openings through which the airbags expand (hereinafter, referred to as “bag-expansion openings”), extend in the longitudinal direction of the vehicle and are formed on the right-hand side portion and the center portion of the outer hood panel as viewed from the passenger compartment. A right-hand side, as viewed from the passenger compartment, airbag is deployed through the right bag-expansion opening to cover the right half of a top surface of a hood, and a left-hand side, as viewed from the passenger compartment, airbag is deployed through the center bag-expansion opening to cover the left half of the top surface of the hood.
In the above-cited reference, the right airbag is deployed in such a way that it first expands upward, through the corresponding bag-expansion opening, by the pressure of a gas supplied from an inflator, and the leading end portion of the airbag then falls down toward the center of the hood. The left airbag is deployed in the same way as the right airbag. For this reason, there is room for improvement in terms of the following two points.
First, while the airbag deployment position at the base portion of the airbag closer to the bag-expansion opening can be controlled or restrained, it is difficult to control or restrain the deployment position of the leading end portion of the airbag distant from the bag-expansion opening. Thus, even if the leading end portion of the right airbag is fastened to the base portion of the left airbag by means of a face-to-face fastener or the like, the possibility still exists that the leading end portion of the right airbag may be raised up, particularly if the vehicle is moving and a wind pressure acts thereon. Such a possibility is increased if the leading end portion of the left airbag that remains unrestrained. Accordingly, it is desirable to enhance the ability of the prior art airbag device to suppress the airbag from being raised up by the wind pressure or other factors.
Secondly, due to the manner of deployment mentioned above, time is taken until the leading end portion of the right airbag falls down toward the base portion of the left airbag. For this reason, if a deployment extent of the airbag is set broad, it becomes difficult to deploy the airbag over the deployment extent quickly . Accordingly, the prior art airbag device has a room for improvement in that the airbag needs to be deployed quickly over a broad extent.